Governments should tax sugary drinks to fight the global epidemics of obesity and diabetes, the World Health Organization said on Tuesday.

A 20 percent price increase could reduce consumption of sweet drinks by the same proportion, the WHO said in a report issued on World Obesity Day.

Bottles of soda are displayed in a cooler at a convenience store Justin Sullivan / Getty Images

Drinking fewer calorie-laden sweet drinks is the best way to curb excessive weight and prevent chronic diseases such as diabetes, although fat and salt in processed foods are also at fault, WHO officials said.

"We are now in a place where we can say there is enough evidence to move on this and we encourage countries to implement effective tax on sugar-sweetened beverages to prevent obesity," Temo Waqanivalu, of WHO's department of Noncommunicable Diseases and Health Promotion, told a briefing.

Obesity more than doubled worldwide between 1980 and 2014, with 11 percent of men and 15 percent of women classified as obese - more than 500 million people, the report said.

"Smart policies can help to turn the tides on this deadly epidemic, especially those aimed at reducing consumption of sugary drinks, which is fuelling obesity rates," former New York mayor Michael Bloomberg, a WHO ambassador for noncommunicable diseases, said in a statement.